This invention relates to a pressure measuring guide wire comprising an elongated flexible shaft with a proximal portion, a distal portion, a lumen extending through the shaft, wall means surrounding said lumen, and aperture means for entry of a pressure medium into the lumen.
Intracoronary pressure recordings give valuable information to the cardiologist to assess both coronary and myocardial flow reserve and collateral blood flow.
The problem of pressure measuring guide wires is to provide an uninterrupted lumen throughout the shaft which has to be highly flexible to conform with the tortuous pathways of the blood vessels; simultaneously, the shaft must have a reasonably high stiffness to assure pushability and torque transmission thereto; and furthermore, the shaft must have a very good kink resistance to avoid the risk of constrictions resulting in modification of the advance of pressure waves through the lumen.
Current pressure measuring guide wires are made of a plastic tube and a stiffening wire. This is, however, very costly and leads to constrictions in the lumen which obstruct the advance of pressure waves in the lumen.
Another approach is shown in the document EP-A1-0419277 which describes a guide wire for use in measuring a characteristic of liquid flow in a vessel comprising a flexible elongate element in the form of a tube with a core wire provided therein the distal extremity of which is tapered and extends beyond the distal end of the tube. The tapered extremity of the core wire extends into a coil spring which is soldered to the tube. The coil spring is formed of two parts which are screwed together and the spring is bonded to the core wire by solder at the region where the two portions of the coil spring are screwed together. A safety wire extends from the joint of the two coils to the distal extremity of the coil spring where it is secured to a transducer carried by the distal end of the coil spring. Front and rear contacts are provided on the transducer and are connected to a two conductor wire which extends rearwardly and interiorly of the coil spring and further extends into the tube between the core wire and the interior of the tube to get out of the tube for connection to a male connector. According to a variant, an insulating sleeve may form a tight fit with the exterior surface of the core wire and it may also fit within the tube to insulate the core from the tube so that the core and the tube and core may serve as separate and independent electrical conductors.
It is an object of this invention to improve over the cited art by means of a pressure measuring guide wire which is easy and inexpensive to manufacture, which is highly versatile while having excellent qualities of pushability and resistance to kinking, and which allows a smooth advance of pressure waves through the lumen.